Means for minimizing commutator flashovers



N. W. STORER. MEANS FOR MINIMIZING GOMMUTATOR FLASHOVERS.

APPucAnoN FILED o'er. 30, 1918.

1,412,546. Patented p 11, 1922.

W(VWWVWW WITNESSES: v INVENTOR Norman WSforer f I BY lU NlTED VSTATES P TENT 1 OFFICE.

NORMAN w. SIORER, or rrrrsiaunen, P NNSYLVANIA, assreNoa r WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, a CORPORATION or PENNSYLVANIA.

To all whom it may corwer' nz Be it known that 1, Norman \V. Sr'onnn,

V a citizen 'of the United States and a resident of Pittsburghyinthe countyot Allegheny and State or Pennsylvaniayhave invented a new and useful Improvement in Means for Minimizing Commutator Flashovers, which the following is a specification My invention relates to means for mini mizing flashovers, and it has for-its object to provide apparatus of the character designated that-may be quickly and inexpensively 4 applied to old machines as well as to new machines and which shallbe effective in operatioinleven under severe working conditions. r

The 'Jsingle. figure of the accompanying drawing is a' diagrammatic view of a dynamo-electrlc mach1ne,together with auxil iary apparatus embodying a preferred torin' of my invention.

Flashovers are of more or less trequency onx the connnutators of dynamo-electric ma chines, particularly :in machines of the highvoltage type This phenomenon is initiated bygiexceptionally severe overloads' or by abrupt changes in load, -the resultant ex -essive. armature-reactance voltage initiating sparks between commutator segments and between segments and the brush, these incipient sparks being carried around the com mutator to a brush set of the other polarity, ionizing a path between brush set-s oi opposite polarity and, therefore, permitting a direct discharge therebetween, with consequent severe injury to the apparatus. The

principal source of energy for the maintenance of vthe violent fiashover arcis the stored energy of the armature and of the magnetic field circuit, the collapse of these magnetic fields liberating energy at a high rate.

It is ofcourse, true that a certain amount oi the flashover energy flows in from the system.- particularly where the machine is operating in parallel with other machines, but the ordinary breakers generally limit the amount" ofene'rgy received from this source to a relatively small amount.

1 find that ifa discharge gap be connected between brusi sets of opposite polarity or between the terminals of a machine, this dis- Specificationof Letters-fatten}. Patented Application am October 30, 1913 Serial o 260,292.

' chargegap being mounted in proximity tov the commutatorjsuriace, the occurrence of a fiashover i'onizesthe'gap, initiating a heavy current discharge between the terminals of the machine,thi s short-circuit path rapidly dissipating the stored energy of the machine as well as furnishing a shunt path around the machine-for energy tending to flow in from the system prior to the opening of the breakers. Preferably, the discharge gap is placed, immediately behind thebrushfset so that the incipient sparks tending to produce a flashovershall also ionize the gap.

Furthermore I find that'jan extremely beneficial effect may be produced by provid ing an auxiliary winding on the field pole pieces, this winding being connected in series with said discharge gap and being so wound that the flow'of current through the gap upon the occurrence of a flashover, causes the'auxiliary winding to magnetically oppose the regular exciting field windings, thereby rapidly killing the field and inductively absorbing its stored energy, thus radically reducing the energy available for the 1 maintenance of the fia'shover are.

Referring to the'drawing for a more detailed understanding of my invention, I show a dynamo-electric machine of the commutator type at 1, this machine comprising an armature 2, an exciting field pole piece 3, and

brushes 4, these brushes bearing on a coinmutator cylinder of usual form 5. The machine 1 maybe either a motor or a generator and is shown as connected between a positive'feeder 6 such as a railway trolley wire and ground at 7. y

The field pole piece 3 is provided with an exciting winding 8, shown as of the shunt type and with an auxiliary winding 9.

A. discharge gap 10 is mounted in proximity to one of the brushes, preferably on the followingside thereof, and comprises horn members 11 and 12; the shortest portion of the discharge gap being in immediate proximity to the surface of the commutator cylinder 5. The discharge gap 10 is connected between the brushes 4l4l through the auxiliary field winding 9 and a resistor 13, this latter element being necessary only in certain cases. Y

Having thus described the arrangement of a system embodying my invention, the op eration thereof is follows. Under normal conditions, the gap 10 is non-conducting and the winding 9 is not energized, the ex-- citing field for the machine 1 being provided by the field winding 8.

Upon the occurrence of abnormal load conditions, severe sparking occurs at the heels oi? the brushes 4t, tending to estab lish a fiashover. ize the discharge gap 10 so that, simultaneously with the initiationoi a fiashover, current fiow takes place across the gap 10 and through the winding 9, this current flow being in such direction that the winding 9 magnetically opposes the winding 8, immediately killing the excitation of the machine. The stored energy of the armature is at once dissipated by the circuit conditions established across its terminals, and the stored energy of the field. circuits is likewise eliminated so that the disastrous effects of the flashover are largely prevented, the How of current from the line being abruptly stopped by the opening of a circuit-- breaker 14,.

lVhile I have shown my inention in its preferred form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various minor changes and n'iodifications without departing from the spirit thereof, and I desire, therefore, that oiily such limitations shall he placed there upon as are imposed by the prior art or are specifically set forth in the appended claims.

I claim as my invention:

1. The combination with a dynamo-electric machine e'tthe commutator type, of means mounted thereon providing a discharge gap, and connecting means for inserting said gap between the terminals of said machine.

2. The combination with a dyna'mmelectric machine of the commutator type, of means providing a discharge gap, connecting means for inserting said. gap between the terminals of said machine, said gap providing means being disposed adjacent to the commutator cylinder of said machine.

it. The combination with a dynamo-elec tric machine oi? the commutator type, of means providing a discharge gap, connecting means for inserting said gap between the terminals of said machine, said discharge gap being mounted in proximity to the surface of the comn'mtating segments, whereby it is ionized and a discharge thereacross ini tiated upon the occurrence of a flashover on the commutator of said machine.

a. The combination with a dynamo-electric machine of the commutator type, of means providing a discharge gap, connecting means for inserting said gap between the terminals of said machine, said discharge These incipient sparks iongap being mounted in proximity to the surface of the commutating segments and at a point immediately behind a brush set, whereby, upon the occurrence of anincipient fiashover at said commutator, said gap will be ionized and a discharge thereacross initiated.

The combination with a dynamo-elecment with said field-exciting means, and

means for energizing said auxiliary field winding so as to magnetically oppose said field exciting means upon the occurrence of a fiashover in said machine.

7. The combination with a dynamo-electric machine of the commutator type provided with field exciting means, of an auxiliary field winding in magnetic alinement with said field exciting means, means providing a discharge gap, connections for inserting said discharge gap between two brush sets of opposite polarity in said machine and in series relation with said auxiliary field winding, and means whereby said discharge gap is ionized and a discharge initiated thereacross upon the occurrence of an incipient flashover in said machine, the consequent direction of current flow in said auxiliary field being such as to demagnetize said field exciting means.

8. The combination with a dynamo-elem tric machine of the commutator type provided with a field-pole bearing an exciting field winding and an auxiliary field wind ing, of means provided with a discharge gap disposed in proximity to the surface of the commutating segments in said machine, and connections from one terminal oi said machine through said gap providing means and auxiliary winding to the remaining terminal of said machine, whereby, upon the occurrence of a flashover at the commutator oi said machine, current flow is initiated through said auxiliary winding, said current flow beng in such direction as to cause said auxiliary winding to magnetically op pose said exciting field winding. I

1 The combination with a dynamo-electric machine of the commutator type provided with a field-pole bearing an exciting field winding and an auxiliary field winding, of means providing a dischargegap in proximity to the surface of the commutating seg ments in said machine immediately behind a brush-set, said connections from one terminal 0% said machine through'said gap and auxfliziry Winding to the remzuning termi- 11:11 of said machine, whereby, upon the oceurrence of an incipient flashover at the commutator of said machine, current flow is inltiated through said auxlhary W nding, said I NORMAN W. STORER. 

